Progressive addition lens and design method therefor

ABSTRACT

A progressive addition lens and the related technology, the progressive addition lens including a near portion for viewing a near distance, a distance portion for viewing a distance farther than the near distance, and an intermediate portion between the near portion and the distance portion and having a progressive refraction function, in which the transmission astigmatism is added to the near portion and the intermediate portion of the distance portion, the near portion, and the intermediate portion, and in the near portion and the intermediate portion to which the transmission astigmatism is added, the progressive addition lens further includes a portion where an amount of horizontal refractive power is greater than an amount of vertical refractive power after subtracting the refractive power for astigmatism correction.

TECHNICAL FIELD

The present invention relates to a progressive addition lens and adesign method thereof. Note that the contents of Japanese PatentApplication No. 2018-185993, Japanese Patent Application No.2018-186038, Japanese Patent Application No. 2019-48645, Japanese PatentApplication No. 2019-48646, Japanese Patent Application No. 2019-48647,and Japanese Patent Application No. 2019-93366, which are the basis ofpriority, are all referred to in this specification.

BACKGROUND ART

FIG. 1A is a diagram illustrating a schematic configuration of aprogressive addition lens.

As illustrated on the left side of FIG. 1A, a progressive addition lensis a lens that has, as an area, a portion of a lens provided in an upperportion of the figure and having a refractive power to view a distanceobject, that is, a distance portion having a refractive power used fordistance vision, a portion of a lens provided in a lower portion of thefigure and having a refractive power to view a near object, that is, anear portion having a refractive power used for near vision, and anintermediate portion provided between the distance portion and the nearportion, and has the refractive power gradually changing between thedistance portion and the near portion.

The area where the refractive power gradually changes is called acorridor. A corridor length is defined as a distance between aprogressive start point where the change in the refractive power startsand a progressive end point where the change in the refractive powerends.

The distance portion is the area of the progressive addition lens thatis the progressive start point and above the progressive start point.The near portion is the area of the progressive addition lens, whichgenerally includes the progressive end point and is located below theprogressive end point. The intermediate portion is the area between thedistance portion and the near portion, and is the area where therefractive power changes progressively.

The diagram on the right side of FIG. 1A is a diagram illustrating thechange in the refractive power along the meridian. In the distanceportion, the refractive power is substantially constant. In the nearportion, the refractive power is substantially constant to view theshort distance object. In the intermediate portion, the refractive poweris gradually changing. A difference between the refractive power thatviews the distance object and the refractive power that views the nearobject is called an addition power ADD (D).

FIG. 1B is a diagram illustrating an example of a distribution oftransmission average refractive power MP and a distribution oftransmission astigmatism AS. Note that the distribution on the left sideof FIG. 1B, that is, the distribution of the transmission averagerefractive power MP is the same as the distribution illustrated in FIG.3A. In addition, the distribution on the right side of FIG. 1B, that is,the distribution of the transmission astigmatism AS is the same as thedistribution illustrated in FIG. 4A.

Here, in the current progressive addition lens technology, theastigmatism is substantially set to zero on a main line of sight notonly in the distance portion and the near portion but also in theintermediate portion in which the refractive power changes. In otherwords, in the current progressive addition lens, the astigmatism issubstantially zero along the main line of sight. A detailed definitionof the main line of sight will be described later.

In such a progressive addition lens, the astigmatism is likely to occurbecause the distance portion and the near portion having differentrefractive powers exist in the same lens. Conventionally, it is designedto remove the astigmatism as much as possible along the meridian.Therefore, in areas other than the meridian, the average refractivepower deviates from the target refractive power, and intrinsicastigmatism and distortion are likely to occur.

The intrinsic astigmatism is unavoidable astigmatism in the progressiveaddition lens that increases on both sides of the intermediate portionand near portion having the meridian therebetween, and a detaileddefinition thereof will be described later.

Meanwhile, in order to reduce the intrinsic astigmatism and distortioncaused by the progressive addition lens, in recent years, a concept of atransmission design has been used in the design of the progressiveaddition lens. This design method takes into consideration actual lightrays (ray tracing) that pass through the lens. The transmission designfocuses on the distributions of the astigmatism and refractive powergenerated by light passing through the lens and entering an eye. Thetransmission design is disclosed in, for example, Patent Literature 1.

The method described in Patent Literature 1 is as follows according to[claim 1] of Patent Literature 1.

After setting the target distribution of transmission refractive powerof the spectacle lens based on the predetermined prescriptioninformation, the spectacle lens is tentatively designed and thedistribution of provisional transmission refractive power is calculated.Then, the difference between the distribution of target transmissionrefractive power and the distribution of provisional transmissionrefractive power is calculated. Then, based on the difference, theoptical correction amount at each control point on the control lineextending from the reference point to the peripheral edge is calculated.A first approximation curve is defined on the closed curve connectingthe control points. A second approximation curve is defined afteradjusting the correction amount of each control point so that eachcontrol point is located on the first approximation curve. The opticalcorrection amount represented by the second approximation curve isconverted into an aspherical additional amount and added to each controlline of the correction target surface. Then, the shape of the correctiontarget surface between each control line is interpolated using apredetermined interpolation method.

CITATION LIST Patent Literature Patent Literature 1: Japanese Patent No.5784418 SUMMARY OF INVENTION Technical Problem

As described above, the method described in Patent Literature 1 iscomplicated. Therefore, a method for obtaining a clear visual fieldrange by a simpler method is desired.

Therefore, an object of an embodiment of the present invention is toprovide a technique for expanding a clear visual field range of a nearportion by a simpler method as compared with a conventional progressiveaddition lens having the same degree of addition power and distancepower.

Solution to Problem

The present inventors have conceived a method for selecting anintermediate portion and a near portion while using a transmissiondesign and then intentionally adding transmission astigmatism to theselocations. Note that this intermediate portion includes a meridianand/or a main line of sight. In addition, the near portion includes themeridian and/or the main line of sight and a near portion measurementreference point N (measurement reference point N).

The meridian and/or the main line of sight and the measurement referencepoint N are locations where a spectacle wearer frequently passes a lineof sight, and adding transmission astigmatism to such locations(moreover, selecting the intermediate portion and the near portioninstead of the distance portion) is not normally performed.

However, the present inventors intentionally added the transmissionastigmatism to these locations by selecting the above intermediateportion and the near portion without being bound by such common sense.As a result, the transmission astigmatism increases at the meridianand/or the main line of sight and the measurement reference point N, butthe sharp changes in the transmission astigmatism can be mitigated. As aresult, it can be acknowledged that the clear visual field range withthe transmission astigmatism of 0.50 D or less can be obtained morewidely than before, and the meridian and/or the main line of sight andthe measurement reference point N can be included in the clear visualfield range. Hereinafter, unless otherwise specified, “compared to theconventional lens” means “compared to the conventional progressiveaddition lens having the same degree of addition power and distancepower”.

The following aspects are made based on the above findings.

A first aspect of the present invention is a progressive addition lens,comprising:

a near portion for viewing a near distance, a distance portion forviewing a distance farther than the near distance, and an intermediateportion provided between the near portion and the distance portion andhaving a progressive refraction function,

in which the transmission astigmatism is added to the near portion andthe intermediate portion of the distance portion, the near portion, andthe intermediate portion, and

in the near portion and intermediate portion to which the transmissionastigmatism is added, the progressive addition lens includes a portionin which an amount of horizontal refractive power is greater than anamount of vertical refractive power after subtracting the refractivepower for astigmatism correction.

In a second aspect of the present invention described in the firstaspect,

the transmission astigmatism having an absolute value exceeding zero and0.25 D or less is added to the near portion and the intermediateportion.

In a third aspect of the present invention described in the first aspector the second aspect,

an absolute value of the value of the transmission astigmatism at ameasurement reference point F of the distance portion after subtractingthe refractive power for astigmatism correction is 0.12 D or less.

In a fourth aspect of the present invention described in any one of thefirst aspect to the third aspect,

an amount of an absolute value of a change amount Δ[D] from a value oftransmission astigmatism at a measurement reference point F of thedistance portion to a value of transmission astigmatism at a measurementreference point N of the near portion is 0.07 to 0.24 times an additionpower ADD[D].

In a fifth aspect of the present invention described in any one of thefirst aspect to the fourth aspect,

the transmission refractive power is added together with thetransmission astigmatism.

A sixth aspect of the present invention is

a design method of a progressive addition lens comprising a near portionfor viewing a near distance, a distance portion for viewing a distancefarther than the near distance, and an intermediate portion providedbetween the near portion and the distance portion and having aprogressive refraction function,

in which the transmission astigmatism is added to the near portion andthe intermediate portion of the distance portion, the near portion, andthe intermediate portion,

in the near portion and intermediate portion to which the transmissionastigmatism is added, the progressive addition lens includes a portionin which an amount of horizontal refractive power is greater than anamount of vertical refractive power after subtracting the refractivepower for astigmatism correction.

After subtracting the refractive power for astigmatism correction in thedistribution (vertical axis y: vertical direction of the lens,horizontal axis x: horizontal direction of the lens, an origin is aprism reference point of the lens) of the transmission astigmatism,

it is preferable that a horizontal width of area a1 where thetransmission astigmatism is 0.50 D or less and y=−14.0 mm is 8 mm ormore, and

a horizontal width of area a2 where the transmission astigmatism is 0.50D or less and y=−20.0 mm is 10 mm or more.

It is preferable that at y=−14.0 mm, there is a portion that becomes theminimum transmission astigmatism in area a1, and

at y=−20.0 mm, there is a portion that becomes the minimum transmissionastigmatism in area a2.

the addition power is preferably 1.5 to 3.0 D.

When viewed the lens from top to bottom, it is preferable that theamount of transmission astigmatism added is not reduced after theaddition of the transmission astigmatism has started.

In addition, when viewed the lens from top to bottom, at least on a mainline of sight from the progressive start point to the measurementreference point N (in the case of meridian, on the meridian up to anintersecting horizontal line), the additional amount is preferably 10%or less or 0.12 D or less even when the additional amount ismonotonically increased after the addition of the transmissionastigmatism has started and the monotonically increased additionalamount is not reduced or is reduced.

According to another aspect of the present invention,

is a method for manufacturing a progressive addition lens, including adesign step which is the design method described in the fifth aspect,and

a manufacturing step for manufacturing a progressive addition lens basedon the design step.

Another aspect of the present invention

is a lens group configured of a plurality of progressive addition lensescomprising a near portion for viewing a near distance, a distanceportion for viewing a distance farther than the near distance, and anintermediate portion provided between the near portion and the distanceportion and having a progressive refraction function,

in which in each progressive addition lens, the transmission astigmatismis added to the near portion and the intermediate portion of thedistance portion, the near portion, and the intermediate portion,

in the near portion and intermediate portion to which the transmissionastigmatism is added, the progressive addition lens includes a portionin which an amount of horizontal refractive power is greater than anamount of vertical refractive power after subtracting the refractivepower for astigmatism correction.

Advantageous Effects of Invention

An embodiment of the present invention can provide a technique forexpanding a clear visual field range of a near portion by a simplermethod, as compared with the conventional progressive addition lenshaving the same degree of addition power and distance power.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a diagram illustrating a schematic configuration of aprogressive addition lens.

FIG. 1B is a diagram illustrating an example of a distribution oftransmission average refractive power MP and a distribution oftransmission astigmatism AS.

FIG. 2 is a diagram for explaining an example of a distribution oftransmission refractive power in a horizontal direction and a verticaldirection in a progressive addition lens.

FIG. 3A is a diagram illustrating a distribution of transmission averagerefractive power corresponding to the conventional progressive additionlens.

FIG. 3B is a diagram illustrating a change in transmission refractivepower in a meridian direction in vertical refractive power (VP),horizontal refractive power (HP), and average refractive power (MP)corresponding to the conventional progressive addition lens.

FIG. 3C is a diagram schematically illustrating changes in horizontaltransmission refractive power, a vertical transmission refractive power,and a transmission average refractive power, which is an average valuethereof, corresponding to the conventional progressive addition lens aty=−4.0 mm.

FIG. 3D is a diagram schematically illustrating the changes in thehorizontal transmission refractive power, the vertical transmissionrefractive power, and the transmission average refractive power, whichis an average value thereof, corresponding to the conventionalprogressive addition lens at y=−14.0 mm.

FIG. 4A is a diagram illustrating a distribution of transmissionastigmatism corresponding to the conventional progressive addition lens.

FIG. 4B is a diagram illustrating a change in transmission astigmatismalong a meridian corresponding to the conventional progressive additionlens.

FIG. 4C is a diagram schematically illustrating a change in horizontaltransmission astigmatism corresponding to the conventional progressiveaddition lens at y=−4.0 mm.

FIG. 4D is a diagram schematically illustrating a change in horizontaltransmission astigmatism corresponding to the conventional progressiveaddition lens at y=−14.0 mm.

FIG. 5A is a diagram illustrating a distribution of transmission averagerefractive power corresponding to the embodiment.

FIG. 5B is a diagram illustrating a change in transmission refractivepower in a meridian direction in vertical refractive power (VP),horizontal refractive power (HP), and average refractive power (MP)corresponding to the embodiment.

FIG. 5C is a diagram schematically illustrating the changes in thehorizontal transmission refractive power, the vertical transmissionrefractive power, and the transmission average refractive power, whichis an average value thereof, corresponding to the embodiment at y=−4.0mm.

FIG. 5D is a diagram schematically illustrating the changes in thehorizontal transmission refractive power, the vertical transmissionrefractive power, and the transmission average refractive power, whichis an average value thereof, corresponding to the embodiment at y=−14.0mm.

FIG. 6A is a diagram illustrating a distribution of transmissionastigmatism corresponding to the embodiment.

FIG. 6B is a diagram illustrating a change in transmission astigmatismalong a meridian corresponding to the embodiment.

FIG. 6C is a diagram schematically illustrating the change in thetransmission astigmatism corresponding to an embodiment at y=−4.0 mm.

FIG. 6D is a diagram schematically illustrating the change in thetransmission astigmatism corresponding to an embodiment at y=−14.0 mm.

FIG. 7A is a distribution map of the finally obtained transmissionastigmatism in the embodiment.

FIG. 7B is a distribution map of the finally obtained transmissionastigmatism in the conventional progressive addition lens.

FIG. 8 is a diagram illustrating pattern 1 in which the transmissionastigmatism is given to a specific area on a design surface.

FIG. 9A is a diagram illustrating the distribution of the transmissionaverage refractive power corresponding to the pattern 1 of theembodiment.

FIG. 9B is a diagram illustrating the distribution of the transmissionastigmatism corresponding to the pattern 1 of the embodiment.

FIG. 9C is a diagram illustrating a change in transmission refractivepower in a meridian direction in vertical refractive power (VP),horizontal refractive power (HP), and average refractive power (MP)corresponding to the pattern 1 of the embodiment.

FIG. 9D is a diagram illustrating a change in transmission astigmatismalong a meridian corresponding to the pattern 1 of the embodiment.

FIG. 10 is a diagram illustrating pattern 2 in which the transmissionastigmatism is given to the specific area on the design surface.

FIG. 11A is a diagram illustrating the distribution of the transmissionaverage refractive power corresponding to the pattern 2 of theembodiment.

FIG. 11B is a diagram illustrating the distribution of the transmissionastigmatism corresponding to the pattern 2 of the embodiment.

FIG. 11C is a diagram illustrating a change in transmission refractivepower in a meridian direction in vertical refractive power (VP),horizontal refractive power (HP), and average refractive power (MP)corresponding to the pattern 2 of the embodiment.

FIG. 11D is a diagram illustrating a change in transmission astigmatismalong a meridian corresponding to the pattern 2 of the embodiment.

FIG. 12 is a diagram illustrating pattern 3 in which the transmissionastigmatism is given to the specific area on the design surface.

FIG. 13A is a diagram illustrating the distribution of the transmissionaverage refractive power corresponding to the pattern 3 of theembodiment.

FIG. 13B is a diagram illustrating the distribution of the transmissionastigmatism corresponding to the pattern 3 of the embodiment.

FIG. 13C is a diagram illustrating a change in transmission refractivepower in a meridian direction in vertical refractive power (VP),horizontal refractive power (HP), and average refractive power (MP)corresponding to the pattern 3 of the embodiment.

FIG. 13D is a diagram illustrating a change in transmission astigmatismalong a meridian corresponding to the pattern 3 of the embodiment.

FIG. 14A is a diagram illustrating a distribution of transmissionaverage refractive power when the ADD changes to 3.00 D in theconventional progressive addition lens.

FIG. 14B is a diagram illustrating a distribution of transmissionastigmatism when the ADD changes to 3.00 D in the conventionalprogressive addition lens.

FIG. 15A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 3.00 D and theadditional amount of the transmission astigmatism changes to 0.30 D inthe embodiment.

FIG. 15B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 3.00 D and the additional amount ofthe transmission astigmatism changes to 0.30 D in the embodiment.

FIG. 16A is a diagram illustrating a distribution of transmissionaverage refractive power when the ADD changes to 1.00 D in theconventional progressive addition lens.

FIG. 16B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 1.00 D in the conventionalprogressive addition lens.

FIG. 17A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 1.00 D and theadditional amount of the transmission astigmatism changes to 0.10 D inthe embodiment.

FIG. 17B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 1.00 D and the additional amount ofthe transmission astigmatism changes to 0.10 D in the embodiment.

FIG. 18A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 2.00 D and theadditional amount of the transmission astigmatism changes to 0.20 D inthe embodiment.

FIG. 18B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 2.00 D and the additional amount ofthe transmission astigmatism changes to 0.20 D in the embodiment.

DESCRIPTION OF EMBODIMENTS

One aspect of the present invention will be described according to thefollowing flow.

1. Gist of technical idea of the present invention

2. Definition

3. Transmission basic design

4. Conventional progressive addition lens

5. Embodiment (horizontal refractive power>vertical refractive power)

5-1. Comparison of target distribution states between conventionaldesign and embodiment

5-2. Comparison of finally obtained lens states between the conventionaldesign and the embodiment

5-3. Addition pattern of transmission astigmatism

5-3-1. Pattern 1

5-3-2. Pattern 2

5-3-3. Pattern 3

6. Modification example (additional amount of transmission astigmatismand variation of ADD in embodiment, and the like)

7. Effect according to one aspect of the present invention

The meanings of symbols and lines in the drawings of the presentapplication are the same. Therefore, only first codes and lines will bedescribed, and the following may be omitted.

1. Gist of Technical Idea of the Present Invention

Prior to a description of a progressive addition lens of an embodimentof the present invention and the related art, the gist of the technicalidea of the present invention will be described.

The reason for the creation of the technical idea of the presentinvention is that it overturns common sense and intentionally addstransmission astigmatism to a place where a spectacle wearer frequentlypasses the line of sight. The portion is an intermediate portion and anear portion. Note that transmission astigmatism is not added to adistance portion. More precisely, the transmission astigmatism is notadded to a fitting point or an eye point FP existing at least in thedistance portion. Details will be defined in [2. Definition] below.

By adding the transmission astigmatism in this way, of course, thetransmission astigmatism increases at a meridian and a measurementreference point N. However, a sharp change in transmission astigmatismis within the entire intermediate portion and near portion. As a result,a clear visual field range in which the transmission astigmatism is 0.50D or less (after subtracting the refractive power for astigmatismcorrection) can be obtained.

That is, according to an embodiment of the present invention, the clearvisual field range of the near portion can be expanded by a methodsimpler than the method described in Patent Literature 1.

In view of the data shown in the embodiments described later, it ispreferable to adopt the following aspects.

Specific examples of the clear visual field range are as follows.

That is, in the preferred progressive addition lens of the embodiment,

after subtracting the refractive power for astigmatism correction in thedistribution (vertical axis y: vertical direction of the lens,horizontal axis x: horizontal direction of the lens, an origin is aprism reference point of the lens) of the transmission astigmatism,

it is preferred to satisfy at least any one of the conditions that ahorizontal width of area a1 where the transmission astigmatism is 0.50 Dor less and y=−14.0 mm is 8 mm or more, and

it is preferable that a horizontal width of area a2 where thetransmission astigmatism is 0.50 D or less and y=−20.0 mm is 10 mm ormore, or

it is more preferably to satisfy both of the conditions.

Further, it is preferable to satisfy at least one of the following twoequations, and it is more preferable to satisfy both equations.

a1>1.7*(ADD)²−10.3*(ADD)+22.6

a2>1.7*(ADD)²−10.5*(ADD)+23.8

Each of the above equations is an approximation curve equation thatseparates a plot of patterns 1, 2, and 3, values of a1 and a2 atvariations, and addition power ADD in the embodiment which is an aspectof the present invention, and a plot of values of a1 and a2 and additionpower ADD in the conventional example, described in the presentspecification.

And,

it is preferable that at y=−14.0 mm, there is a portion that becomes theminimum transmission astigmatism in the area a1, and

at y=−20.0 mm, there is a portion that becomes the minimum transmissionastigmatism in the area a2.

The transmission astigmatism having an absolute value exceeding zero and0.25 D or less is preferably added to the near portion and theintermediate portion. Note that as shown by the test results of thesubjective evaluation described in the basic application, the additionof the transmission astigmatism of at least 0.75 D or less is permitted.

In addition, the absolute value of the value of the transmissionastigmatism at the measurement reference point F of the distance portionafter subtracting the refractive power for astigmatism correction ispreferably 0.12 D or less. That is, since transmission astigmatism isnot added to the distance portion, the absolute value of thetransmission astigmatism is low, and the clear visual field range can beobtained even though the transmission astigmatism is added to theintermediate portion and the near portion.

The addition power ADD of the progressive addition lens according to theembodiment is not particularly limited. However, since the additionpower ADD is relatively high (for example, in the range of 1.5 to 3.0 D)and the transmission astigmatism also tends to increase, even if theaddition power ADD is set to be high, the embodiment is applied, and asa result, there is a big advantage that the clearer visual field rangecan be obtained than before.

In the progressive addition lens, there is a trade-off relationshipbetween an error in the average refractive power and the astigmatismregardless of the surface shape or the transmission. The relationshipbecomes more pronounced off the center of the progressive addition lens.

In the embodiment to be described later, among the above two, theastigmatism is emphasized, that is, in order to suppress the increase inthe astigmatism, as described above, the progressive addition lens isset to include a portion where the amount of horizontal refractive poweris greater than the amount of vertical refractive power aftersubtracting the refractive power for astigmatism correction.

Incidentally, three types of addition patterns of transmissionastigmatism are prepared for the embodiment (patterns 1, 2, and 3described later). Note that in the embodiment itself, the transmissionastigmatism is added to the meridian, and the amount of transmissionastigmatism is adjusted so that the surface shape becomes smooth in thevicinity of the meridian.

In pattern 1 (FIG. 8), the transmission astigmatism is added in afan-shaped area that extends downward.

In pattern 2 (FIG. 10), a certain amount of transmission astigmatism isadded to almost the lower half of the design surface.

In pattern 3 (FIG. 12), the transmission astigmatism is added byproviding a plurality of control points in the lens and controlling thecurvature at the control points using a spline function.

Note that the results when various addition patterns of transmissionastigmatism are applied to the embodiment are also shown.

The results of the embodiment in the case of pattern 1 are illustratedin FIGS. 9A to 9D.

The results of the embodiment in the case of pattern 2 are illustratedin FIGS. 11A to 11D.

The results of the embodiment in the case of pattern 3 are illustratedin FIGS. 13A to 13D.

Incidentally, in the patterns 1 to 3, when viewed the lens from top tobottom, the amount of transmission astigmatism added is notsubstantially reduced after the addition of the transmission astigmatismhas started. That is, the additional amount increases to the peripheraledge of the lens as in the pattern 1 (FIG. 8), increases to apredetermined additional amount as in pattern 2 (FIG. 10) and pattern 3(FIG. 12), and then becomes a fixed additional amount. In other words,when viewed the lens from top to bottom, the additional amount increasesmonotonically after the addition of the transmission astigmatism hasstarted, and the monotonously increased additional amount does notdecrease or is 10% or less of the additional amount or is 0.12 D or lesseven if the monotonously increased additional amount decreases. Notethat considering the possibility that the additional amount at theperipheral edge of the lens fluctuates due to the lens processing andthe additional amount decreases when the fluctuation occurs, it is alsopreferable to specify as follows.

In the “at least from the progressive start point to the measurementreference point N (in the case of the meridian, up to the intersectinghorizontal line), the additional amount increases monotonically afterthe addition of the transmission astigmatism has started, and themonotonously increased additional amount does not decrease or it is 10%or less of the additional amount or is 0.12 D or less even if themonotonously increased additional amount decreases.”

The addition of the transmission astigmatism causes the decrease in thetransmission refractive power. The average refractive power isrepresented by spherical refractive power+cylindrical power/2. Forexample, when the transmission astigmatism is added by decreasing thevertical refractive power, the average refractive power decreases due toa decrease in a value of cylindrical power in the above equation for theaverage refractive power in the vertical direction. This means that avalue lower than the addition power of the prescribed value is obtainedas the addition power. Therefore, in the present embodiment, thetransmission refractive power is added together with the transmissionastigmatism so as to compensate for the decrease in the refractive poweraccompanying the addition of the transmission astigmatism and to realizethe planned addition power. The additional amount of the transmissionrefractive power may be determined according to the decrement in therefractive powers and the planned addition power.

Hereinafter, although not specified, all the distribution maps of thetransmission average refractive power described in the presentspecification are after the addition of the transmission refractivepower described above is performed.

A specific example of adding the transmission refractive power togetherwith the transmission astigmatism is as follows. The additional amountof the transmission astigmatism may be determined in advance. A lensdesign that in advance considers the change in the refractive poweraccompanying the addition of the transmission astigmatism is prepared.By adding the predetermined transmission astigmatism to the lens design,it may be set so that a target addition power can be obtained.

As a result, in all the distribution maps of the transmission averagerefractive power described in the present specification, the initiallyset addition power can be realized even after the transmissionastigmatism is added.

Note that in the progressive addition lens to which the transmissionastigmatism is added, at the measurement reference point N of the nearportion, if a value of distance power S+addition power ADD described ona lens bag or the like due to the change in the refractive power by theaddition, that is, the deviation from the near power is partiallycompensated, it is considered that the addition of the transmissionrefractive power is performed. As an example, in the state in which thedeviation is finally not present in the progressive addition lens or thestate in which the deviation amount is within ±0.12 D even if thedeviation is present, it is considered that the addition of thetransmission refractive power is performed.

Hereinafter, the progressive addition lens and the design method thereofaccording to an embodiment will be described in detail. Note that theembodiment described in the present specification corresponds toEmbodiment 1 in the basic application. First, in order to understand theembodiment, the definition of each item will be described.

2. Definition

In the present specification, generally, as a wording indicating thedegree of refraction of a lens, so-called power, and the refractivepower instead of power is used.

In this specification, the terms three kinds of “astigmatism” are usedto clarify the difference in meaning.

The first term is “prescription astigmatism”. The prescriptionastigmatism relates to prescription data for correcting eye defects (eyeastigmatism) and corresponds to a columnar refractive power ofprescription data.

The second term is “intrinsic astigmatism”. The intrinsic astigmatismrelates to astigmatism caused by a surface shape of an optical lens andhas the same meaning as the term “astigmatism” commonly used in theoptical lens design. As used herein, the intrinsic astigmatismoriginally refers to astigmatism that is inherently indispensable due tothe surface shape of the progressive addition lens, that is, anaspherical component constituting a progressive surface.

The third term is “additional astigmatism”. The additional astigmatismis the main component of the embodiment, and is the astigmatismintentionally added to the distribution of the transmission astigmatismdifferent from the prescription astigmatism (refractive power forastigmatism correction and astigmatism power) when setting thedistribution of the transmission target refractive power in the designstage of the progressive addition lens. For convenience of explanation,in this specification, the additional astigmatism is also referred to asthe addition of the transmission astigmatism.

In the present specification, the transmission astigmatism added is theabove-mentioned additional astigmatism. The additional astigmatism canbe realized by adding the surface astigmatism to at least one of thesurface on the object side and the surface on the eyeball side in theprogressive addition lens. As a result, the transmission astigmatism isadded as the progressive addition lens as a whole.

Note that the expression “transmission refractive power” also refers tothe progressive addition lens in which the surface refractive power isadded to at least one of the surface on the object side and the surfaceon the eyeball side.

The transmission astigmatism is the value obtained by subtracting theminimum refractive power from the maximum refractive power at apredetermined location on the progressive addition lens in the wearingstate.

In the present specification, the value of the “additional amount of thetransmission astigmatism” indicates the maximum value of thetransmission astigmatism to be added. In the embodiment described later,when viewed the lens from top to bottom, the maximum value (0.50 D) issuddenly added at the start of the addition of the transmissionastigmatism, while the patterns 1, 2 and 3 described later are not theabove case. In other words, the fact that the additional amount of thetransmission astigmatism is 0.50 D means that the maximum value is 0.50D, and is an expression that allows an additional amount to be less than0.50 D between the beginning portion of the addition of the transmissionastigmatism as in the patterns 1, 2, and 3 and the arrival portion ofthe maximum value.

Note that the lower limit of this maximum value is not particularlylimited, but is preferably 0.08 D, and more preferably 0.10 D. The upperlimit of the maximum value is not particularly limited as described in[1. Gist of technical idea of the present invention], but is preferably0.75 D, and more preferably 0.25 D.

In the progressive addition lens, the “main line of sight” is a locusline on the lens surface where the line of sight moves when an object isviewed from the front, in the distance portion used for the distancevision, the near portion used for the near vision, and the intermediateportion located between the distance portion and the near portion.

The “meridian” is a vertical line that is orthogonal to a horizontalline connecting positions of two hidden marks provided on theprogressive addition lens and passes through a midpoint of the positionsof the two hidden marks. The meridian corresponds to the y axis of thedistribution map illustrated in each figure of the present application.

The line of sight of the eye is closer to a nasal side (inner side) inthe near vision. Therefore, the main line of sight in the intermediateportion and near portion is closer to the nasal side (medial side) withrespect to the meridian. The amount of main line of sight by the nasalside with respect to such a meridian is called an inward adjustmentamount. Therefore, when the inward adjustment amount is 0, the main lineof sight matches the meridian. Even in the distance portion, the mainline of sight matches the meridian.

In this specification, in order to make the explanation easy tounderstand, an example of setting the inward adjustment amount to 0 isgiven at the design stage of the lens. In the present specification, thedesign stage of the lens is also referred to as a target distributionstate. On the other hand, an example is given in which the inwardadjustment amount is set to a value greater than 0 for a lens obtainedthrough the design and manufacture of the lens. In the presentspecification, this state is also referred to as a finally obtained lensstate. However, the present invention is not limited to these examples.

The “distance portion measurement reference point” refers to giving theprogressive addition lens the spherical refractive power and thecolumnar refractive power described in the prescription data of thewearer information. The spherical refractive power refers to theso-called spherical power S (distance power S), and the columnarrefractive power refers to the so-called astigmatic power C. Thedistance portion measurement reference point (hereinafter, also simplyreferred to as measurement reference point F or point F) is located on,for example, the meridian, and is located at a position 8.0 mm away fromthe horizontal line connecting the positions of the two hidden marks tothe distance portion side.

The “fitting point or eye point (FP)” is the position through which theline of sight passes when facing right in front, when wearing theprogressive addition lens. Generally, it is placed at a position few mmbelow the measurement reference point F. The change in the refractivepower occurs below this FP. The point at which the change in theprogressive power starts is also called the progressive start point. Inthe embodiment, a geometric center GC further below the FP and theprogressive start point are matched, and the prism reference point isalso matched.

The “transmission astigmatism is not added to the distance portion”described in [1. Gist of technical idea of the present invention] meansthat transmission astigmatism is not added to at least the FP existingin the distance portion. Since off-axis aberration occurs in the lensperipheral area of the distance portion, the aspherical correction maybe applied to the lens peripheral area. Therefore, it is not necessaryto bring about the state in which the transmission astigmatism is notadded to the entire distance portion. Preferably, “transmissionastigmatism is not added to the distance portion” means that notransmission astigmatism is added at least between the measurementreference point F and the FP (preferably the GC further down).

The “adding the transmission astigmatism to the intermediate portion andthe near portion” means adding the transmission astigmatism to at leasta part of the intermediate portion and adding the transmissionastigmatism to at least a part of the near portion.

When the additional state of the transmission astigmatism is defined asa numerical value, it indicates the state in which the value from theabsolute value Δ2 of the transmission astigmatism at the measurementreference point F (reference numeral 16 in FIG. 2) of the distanceportion to the absolute value Δ1 of the transmission astigmatism at anypoint of the intermediate portion or the near portion increases.

As shown in patterns 1 and 3 of the addition of the transmissionastigmatism described later, the transmission astigmatism is notnecessarily added to the entire area below the horizontal line passingthrough the progressive start point and the geometric center GC.

Further, when viewed the lens from top to bottom, it is not necessary tostart the addition of the transmission astigmatism from directly belowthe FP, directly below the progressive start point, directly below theGC, or directly below the prism start point. It is sufficient to startthe addition of the transmission astigmatism between the progressivestart point and the measurement reference point N. The transmissionastigmatism may not be added to the portion closer to the distanceportion in the intermediate portion, and the transmission astigmatismmay be added only to the portion closer to the near portion.

However, it is preferable to add the transmission astigmatism on themain line of sight (and/or meridian) passing through the intermediateportion and the near portion below the portion where the addition of thetransmission astigmatism has started. At least, it is preferable to addthe transmission astigmatism on the main line of sight from the portionbetween the progressive start point and the measurement reference pointN to the measurement reference point N. In terms of the meridian, it ispreferable to add at least the transmission astigmatism on the entiremeridian from the portion (for example, within a radius of 5 mm from theGC, preferably within 3 mm) between the progressive start point and themeasurement reference point N to the horizontal line intersecting themeasurement reference point N. Since the FP and the progressive startpoint normally exist on the meridian (on the y axis), the horizontalline is not used, but even if the FP and the progressive start point donot exist on the meridian, by using the horizontal line, it is possibleto define the above “whole meridian”.

The “near portion measurement reference point” refers to a point inwhich the addition power ADD is added to the spherical refractive powerdescribed in the prescription data of the wearer information, and refersto point in which spherical refractive power+ADD is first realized whenviewed the lens from top to bottom. The near portion measurementreference point (hereinafter, also simply referred to as measurementreference point N or point N) is also located on the meridian.

By the way, the prescription data of the wearer information is describedin the lens bag of the progressive addition lens. That is, if there isthe lens bag, it is possible to specify the lens object as the object ofthe progressive addition lens based on the prescription data of thewearer information. The progressive addition lens is usually made as theset with the lens bag. Therefore, the progressive addition lens to whichthe lens bag is attached also reflects the technical idea of the presentinvention, and the same applies to the set of the lens bag and theprogressive addition lens.

In addition, the positions of measurement reference point F, the fittingpoint or the eye point FP, and the measurement reference point N can bespecified by referring to a remark chart or a centration chart issued bythe lens manufacturer.

In the transmission distribution of the distribution of the transmissionaverage refractive power or the distribution of the transmissionastigmatism illustrated in the following figures, the transmissionaverage refractive power and the transmission astigmatism formed bypassing light rays through each position of the progressive surface ofthe progressive refraction lens are shown at the position of theprogressive surface through which the light rays pass.

Further, in the transmission distribution of the transmission averagerefractive power or the transmission astigmatism, the location on thetransmission distribution corresponding to the distance portion definedon the lens surface is expressed as “the portion corresponding to thedistance portion”. For convenience of explanation, the “portioncorresponding to the distance portion” is also simply expressed as the“distance portion”. Unless otherwise specified, the “distance portion”refers to the above “portion corresponding to the distance portion”.

Note that the distance portion is not particularly limited as long as itis an area for viewing a distance farther than the near distance. Forexample, it may be an area for viewing a predetermined distance (about 1m) instead of infinity. Examples of a spectacle lens provided with suchan area include an intermediate-near lens corresponding to an objectdistance of an intermediate distance (1 m to 40 cm) to a near distance(40 cm to 10 cm) and a corresponding near-near lens within the neardistance.

In any of the above spectacle lenses, the intermediate portion and thenear portion include an astigmatism adjustment area (area R illustratedin FIG. 2) in which the surface shapes of the near portion and theintermediate portion are adjusted. Of the distribution of thetransmission astigmatism generated by light rays transmitted throughthis spectacle lens, the positions of the maximum refractive power inthe intermediate portion and the near portion is approximately the sameposition in the horizontal direction. That is, the position of themaximum refractive power in the intermediate portion and the nearportion has substantially the same value on the x axis in terms ofcoordinates.

The “position of the maximum refractive power” is a position where thehorizontal refractive power and the vertical refractive power orthogonalto the horizontal direction each are the maximum refractive powers. Thefact that the position of the maximum refractive power where thehorizontal refractive power and the vertical refractive power are themaximum refractive power are substantially the same means that the casewhere the horizontal refractive power and the vertical refractive powerare separated within 2 mm is included as an allowable range.

According to the embodiment described later, the difference between themaximum refractive power in the horizontal direction and the maximumrefractive power in the vertical direction in the intermediate portionand the near portion is different from the difference between thehorizontal refractive power and the vertical refractive power at thepoint corresponding to the distance portion measurement reference point.The absolute value of the difference is preferably 0.25 D or less.

Note that it is preferable that the difference in the maximum refractivepower is different from the difference between the horizontal refractivepower and the vertical refractive power at a point corresponding to thedistance portion measurement reference point even in the locationcorresponding to the location along the meridian in the astigmatismadjustment area.

“In the near portion and the intermediate portion to which thetransmission astigmatism is added, including the portion where theamount of horizontal refractive power is greater than the amount ofvertical refractive power after subtracting the refractive power forastigmatism correction” means that in at least a part of the portionwhere the transmission astigmatism is added in the near portion and theintermediate portion, after subtracting the refractive power forastigmatism correction, the amount of horizontal refractive power isgreater than the amount of vertical refractive power. Obviously, in theportion where the transmission astigmatism is added, the amount ofhorizontal refractive power may always be greater than the amount ofvertical refractive power. Also, in the near portion and theintermediate portion, at least on the main line of sight (and/ormeridian) (preferably at least from the progressive start point to themeasurement reference point N), it is preferable that the amount ofhorizontal refractive power is greater than the amount of verticalrefractive power.

Further, the y direction referred to in the present specification is adirection along the meridian and is a vertical direction. The upper sideof the lens in the worn state is set as a +y direction, and the lowerside of the lens is set as a −y direction. The x direction is thedirection orthogonal to the meridian and is the horizontal direction.When facing the wearer, the right side of the lens is set as a +xdirection and the left side of the lens is set as a −x direction.

3. Transmission Basic Design

Hereinafter, the distribution of the transmission astigmatism in thetransmission basic design used in the embodiment will be described. Theknown technique (for example, the contents described in PatentLiterature 1) may be adopted for the transmission basic design itself.

The transmission astigmatism can be calculated from the differencebetween the tangential transmission refractive power (T) in the verticaldirection (y direction) and the sagittal transmission refractive power(S) in the horizontal direction (x direction). At that time, thetransmission astigmatism in the case of the distance vision iscalculated from T and S in the case of the distance vision, and thetransmission astigmatism in the case of the near vision is alsocalculated from T and S in the case of the near vision.

Using the components (T and S in each of the distance vision and thenear vision) of the astigmatism generated by the light rays passingthrough each position of the progressive addition lens, the distributionof the average refractive power MP and the distribution of theastigmatism AS can be created. This distribution is the distribution ofthe transmission astigmatism and the distribution of the transmissionaverage refractive power.

The lens surface shape is adjusted so that the distribution of thetransmission astigmatism and the distribution of the transmissionaverage refractive power approach the distribution of the transmissionastigmatism and the distribution of the transmission average refractivepower defined in advance as a target.

At that time, it is preferable that the distribution of the transmissionastigmatism and the distribution of the transmission average refractivepower are the distributions calculated from the surface shape of theprogressive addition lens using at least the information of acorneal-lens apex distance, an anteversion angle, and a front angle.

Once the lens surface shape has been calculated to approach the targettransmission distribution (distribution of astigmatism and distributionof average refractive power), the processing machine can manufacture thelens.

Before explaining the progressive addition lens of the embodiment, theembodiment and the conventional progressive addition lens which is thecomparison target will be described.

4. Conventional Progressive Addition Lens

FIGS. 3 and 4 are diagrams illustrating the progressive addition lens inwhich the conventional transmission basic design is performed. FIGS. 3Ato 3D are diagrams illustrating the distribution of the transmissionaverage refractive power and the changes in the transmission averagerefractive power (MP) and the astigmatism (VP and HP) along the vertical(along the meridian) and horizontal directions. Note that the verticalaxis y indicates the vertical direction of the lens, the horizontal axisx indicates the horizontal direction of the lens, and the originindicates the prism reference point of the lens.

FIGS. 4A to 4D are diagrams illustrating the distribution of thetransmission astigmatism and the change in the transmission averagerefractive power and the transmission astigmatism along the vertical andhorizontal directions.

The surface illustrating the transmission average refractive power andthe transmission astigmatism is a virtual far point sphere on a side ofan eye to which light rays passing through the lens are projected. Theword “virtual” means that the surface is not the actual surface of thelens. Here, the transmission average refractive power and thetransmission astigmatism are different from the surface averagerefractive power and the surface astigmatism refractive power (in theopposite sense of a radius of curvature of the lens surface), and arethe average refractive power and the intrinsic astigmatism that aregenerated on the side of the eye.

Hereinafter, the conventional progressive addition lens will bedescribed with reference to FIGS. 3 and 4.

FIG. 3A is a diagram illustrating the distribution of the transmissionaverage refractive power corresponding to the conventional progressiveaddition lens. The conditions adopted in FIG. 3A are listed below.

-   -   Lens diameter: 60 mm    -   Inward adjustment amount: 0.0 mm    -   S (spherical refractive power at distance portion measurement        reference point): +0.00 D    -   C (columnar refractive power): +0.00 D    -   ADD: 2.00 D    -   Corridor length: 18 mm

Arrows “A” and “B” indicate a horizontal width of an area that is equalto or more than a given refractive power (for example 1.00 D).

The arrow “A” corresponds to a portion of y=−14.0 mm, that is, arepresentative portion of the near portion.

The arrow “B” corresponds to a portion of y=−20.0 mm, that is, arepresentative portion representing a downward portion of the nearportion. Note that y=−20.0 mm is sufficient as a lower limit value tosecure the near portion when the supply conditions of the lens to theframe are taken into consideration.

FIG. 3B illustrates the change in the transmission refractive poweralong the meridian corresponding to the conventional progressiveaddition lens. The vertical axis shows a position [mm] in the ydirection, and the horizontal axis shows the average refractive power[D] whose value changes according to the addition power ADD [D].

In addition, in FIG. 3B, a line of the vertical refractive power (VP) isa dotted line, a line of the horizontal refractive power (HP) is abroken line, and a line of the average refractive power (MP) is a solidline. The MP is the average of the VP and HP.

According to the line of the MP illustrated in FIG. 3B, a corridorlength from the progressive start point at y=4.0 mm to the progressiveend point at y=−14.0 mm where the average refractive power reachesaddition power (ADD) 2.00 D indicates 18 mm.

The area between the progressive start point and the progressive endpoint corresponds to the intermediate portion. The area above theprogressive start point corresponds to the distance portion. The areabelow the progressive end point corresponds to the near portion.

FIGS. 3C and 3D are diagrams schematically illustrating the changes inthe horizontal transmission refractive power, the vertical transmissionrefractive power and the transmission average refractive power, which isan average value thereof, corresponding to the conventional progressiveaddition lens at y=−4.0 mm and y=−14.0 mm. The vertical axis shows therefractive power [D], and the horizontal axis shows the position [mm] inthe x direction (horizontal direction). y=−4.0 mm is set as therepresentative value of the intermediate portion, and y=−14.0 mm is setas the representative value of the near portion.

FIGS. 3B to 3D illustrate that there is almost no transmissionastigmatism along the meridian. At least transmission astigmatism is notadded. This is a major difference from the embodiment to be describedlater, that is, the method for adding transmission astigmatism to anintermediate portion and a near portion.

FIG. 4A is a diagram illustrating the distribution of the transmissionastigmatism corresponding to the conventional progressive addition lensunder the conditions adopted in FIG. 3A. Hereinafter, unless otherwisespecified, the distribution of the transmission astigmatismcorresponding to the distribution of the transmission refractive poweris the distribution under the conditions adopted in the distribution ofthe transmission refractive power.

The area “a” is used as an indicator of the clear visual field range.The clear visual field range is the visual field range in which thewearer can clearly see through the progressive addition lens. The clearvisual field range is defined as a non-occluded area sandwiched by aspecific contour line of the transmission astigmatism. In this example,the value of the transmission astigmatism, which indicates the clearvisual field range, is 0.50 D. This value is not limited to 0.50 D andmay be, for example, 0.25 D. The value of the transmission astigmatismused as an indicator preferably does not exceed 0.50 D.

As will be described in detail later, the arrow of the area “a” is usedto indicate that a clear visual field range can be secured widely in ahorizontal direction with a progressive addition lens according to oneaspect of the present invention, as compared with the conventionalprogressive addition lens.

The two arrows in area a are y=−14.0 mm (representative portion of thenear portion: area a1), y=−20.0 mm (representative portion representingthe lower portion of the near portion: area a2), as described withrespect to FIG. 3A related to the distribution of the transmissionrefractive power. The area a1 and area a2 are also collectively referredto as the area “a′”.

The area surrounded by a circle of symbol b in FIG. 4A corresponds tothe area where the maximum transmission astigmatism exists, and a valueof transmission astigmatism of an area b is the maximum. Note that thearea “b” is an area on the side of the area “a”. The area “b” is an areawith an x coordinate whose absolute value is greater than an xcoordinate of the area “a”. In addition, the area “b” is also an areathat includes the portion of the maximum transmission astigmatism.

FIG. 4B is a diagram illustrating the change in the transmissionastigmatism along the meridian corresponding to the conventionalprogressive addition lens. The vertical axis indicates the position [mm]in the y direction, and the horizontal axis indicates the transmissionastigmatism D. FIG. 4B illustrates that the transmission astigmatismalong the meridian is substantially zero corresponding to FIG. 3B.

FIGS. 4C and 4D are diagrams schematically illustrating a change inhorizontal transmission astigmatism corresponding to the conventionalprogressive addition lens at y=−4.0 mm and y=−14.0 mm. The vertical axisindicates the transmission astigmatism [D], and the horizontal axisindicates the position [mm] in the x direction.

According to FIGS. 4C and 4D, the value of the transmission astigmatism(x=0.0 mm) along the meridian is almost zero. This is a major differencefrom the embodiment to be described later, that is, a distribution afteradding transmission astigmatism to an intermediate portion and a nearportion.

Hereinafter, embodiments of a progressive refractive lens 10 illustratedin FIG. 2 will be described. In the following embodiment, thetransmission astigmatism is added to the meridian. Note that forconvenience of explanation, contents that overlap with the contentsexplained in the above (conventional progressive addition lens) columnwill be omitted.

5. Embodiment (Horizontal Refractive Power>Vertical Refractive Power)

Hereinafter, embodiments of the present invention will be described. Asdescribed in the column of (gist of technical idea of the presentinvention), astigmatism is emphasized, that is, in order to suppress theincrease in astigmatism, in the embodiment, the progressive additionlens is set to include a portion where the amount of horizontalrefractive power is greater than the amount of vertical refractive powerafter subtracting the refractive power for astigmatism correction. Notethat in the embodiment, the transmission astigmatism of 0.50 D is addedon the meridian of the intermediate portion and the near portion.

FIGS. 5 and 6 are an embodiment of the progressive refractive lens 10illustrated in FIG. 2, and are diagrams illustrating an embodiment inwhich in the distribution of the transmission astigmatism, thetransmission astigmatism is added to the portion corresponding to thenear portion and the intermediate portion, and the vertical refractivepower is smaller than the horizontal refractive power.

FIGS. 5A to 5D are diagrams illustrating an example of the distributionof the transmission average refractive power in embodiment and anexample of the change in the transmission average refractive power andthe transmission astigmatism along the vertical and horizontaldirections.

FIGS. 6A to 6D are diagrams illustrating an example of the distributionof the transmission astigmatism in embodiment and an example of thechange in the transmission average refractive power and the transmissionastigmatism along the vertical and horizontal directions.

This will be described below with reference to FIGS. 5 and 6.

FIG. 5A is a diagram illustrating the distribution of the transmissionaverage refractive power corresponding to the embodiment. Since theconditions adopted in FIG. 5A are the same as the conditions adopted inthe above (conventional progressive addition lens) column, thedescription thereof will be omitted.

FIG. 5B illustrates the change in the transmission refractive poweralong the meridian corresponding to the embodiment. The vertical axisshows a position [mm] in the y direction, and the horizontal axis showsthe average refractive power [D] whose value changes according to theaddition power ADD [D].

In FIG. 5B, the average refractive power (MP) rises toward the lowerside of the lens. The reason is as follows.

At y=−14.0 mm which is the progressive end point, the difference betweenthe vertical refractive power (HP) and the horizontal refractive power(VP) is set to 0.50 D. In the embodiment, the horizontal refractivepower (VP) is set to be greater than the vertical refractive power (HP),at least on the meridian. Specifically, for the meridian below theprogressive start point, the horizontal refractive power increases by0.25 D, the vertical refractive power decreases by 0.25 D, and thetransmission astigmatism is added by 0.50 D. At that time, the averagerefractive power (MP) increases downward, and the average refractivepower is set to be the value of S+ADD (2.0 D in this case) at themeasurement reference point N. This setting adds the transmissionastigmatism of 0.50 D in the intermediate and near portions.

Since this astigmatism works in the direction of canceling the intrinsicastigmatism that originally exists in the progressive part, the clearvisual field area of the near portion is widened. The reason is asfollows.

In the case of the progressive addition lens, the intrinsic astigmatismexisting in the progressive portion has a relationship of verticalrefractive power>horizontal refractive power because the refractivepower increases toward the lower side of the lens.

On the other hand, the transmission astigmatism added in the embodimenthas a relationship of horizontal refractive power>vertical refractivepower.

As a result, the transmission astigmatism added in the embodimentcancels the intrinsic astigmatism existing in the progressive portion.

FIGS. 5C and 5D are diagrams schematically illustrating the changes inthe horizontal transmission refractive power, the vertical transmissionrefractive power, and an average value thereof at y=−4.0 mm and y=−14.0mm, respectively. The vertical axis shows the refractive power [D], andthe horizontal axis shows the position [mm] in the x direction.

In FIGS. 5C and 5D, the vertical refractive power is smaller than thehorizontal refractive power in the range from about x=−5.0 mm to x=5.0mm near the meridian. On the other hand, in the area outside the aboverange, the vertical refractive power is greater than the horizontalrefractive power.

In FIG. 5D, the vertical refractive power decreases toward thesurrounding area, so the transmission astigmatism around the nearportion decreases. The reduction in the transmission astigmatism will bedescribed later by comparing FIGS. 4A and 6A.

In other words, the transmission astigmatism added is 0.50 D, and whenviewed along the meridian in the intermediate portion and the nearportion, the vertical refractive power is smaller than the horizontalrefractive power. This is the direction in which the distortion peculiarto the progressive surface is eliminated.

FIG. 6A illustrates the distribution of the transmission astigmatismcorresponding to the embodiment.

FIG. 6B illustrates the change in the transmission astigmatism along themeridian corresponding to the embodiment. The vertical axis indicatesthe position [mm] in the y direction, and the horizontal axis indicatesthe transmission astigmatism (D) transmitted.

FIG. 6B illustrates that the transmission astigmatism of a predeterminedamount of 0.50 D is intentionally added along the meridian in theintermediate portion and the near portion. The transmission performanceparameter corresponding to the sum of the prescription astigmatism andthe predetermined amount of additional astigmatism included in theprescription data is 0.50 D.

FIGS. 6C and 6D are diagrams schematically illustrating the change inthe transmission astigmatism at y=−4.0 mm and y=−14.0 mm, respectively.The vertical axis is the transmission astigmatism [D], and thehorizontal axis is the position [mm] in the x direction.

In FIGS. 6C and 6D, the transmission astigmatism of about 0.50 D isadded along the meridian. At y=−14.0 mm, where the near portionreference point (N) of the near portion is set, the additional amount ofthe transmission astigmatism reaches 0.50 D.

In the embodiment, the transmission astigmatism is shown to be formed onthe side of the eye and added to the portion corresponding to the nearportion and the intermediate portion. Further, in one example, thevertical refractive power is smaller than the horizontal refractivepower in the portion corresponding to one point of the near portion. Inanother example, in the meridian (or main line of sight) of theintermediate portion and near portion, the vertical refractive power issmaller than the horizontal refractive power. In other words, thetransmission astigmatism is added so that the vertical refractive poweris smaller than the horizontal refractive power, thereby providing thetransmission astigmatism to the eye.

By adding the transmission astigmatism as described above, it ispossible to control the width of the enlarged clear visual field rangein the near portion. The clear visual field range is an area where thetransmission astigmatism is a predetermined threshold value or less.

(5-1. Comparison of Target Distribution States Between ConventionalDesign and Embodiment)

The conventional design using the conventional transmission basic design(FIG. 4A) and the embodiment (FIG. 6A) are compared in the distributionof the transmission astigmatism. These distributions are handled as areference when designing the actual surface of the finally obtainedlens, and are used as the target distribution of the transmissionastigmatism.

FIGS. 4A and 6A show a comparison of the distributions of thetransmission astigmatism between the conventional design (FIG. 4A) andthe embodiment (FIG. 6A). By referring to the area “a” of bothdistributions of the transmission astigmatism, it can be seen that theclear visual field range of the near portion of the embodiment is widerthan the conventional clear visual field range.

The width (width by image measurement, the same applies hereinafter) ofthe clear visual field range in the distribution of the transmissionastigmatism of the embodiment is 10.65 mm at y=−14.0 mm (a1) and 13.55mm at y=−20.0 mm (a2).

In the conventional design, the width is 8.30 mm at y=−14.0 mm (a1), and10.00 mm at y=−20.0 mm (a2).

Table 1 below describes a summary of the results of the widths of theclear visual field range at a position of y=−14.0 mm (a1) and a positionof y=−20.0 mm (a2) when the addition power is 2.00 D. Table 1 alsodescribes other results described below.

TABLE 1 ADD = 2.00 D Area a1 Width of Area a2 Width of (y = −14.0 mm) (y= −20.0 mm) Conventional 8.30 10.00 Example Embodiment 10.65 13.55Pattern 1 10.65 15.97 Pattern 2 10.65 13.55 Pattern 3 9.91 13.55 Unit:mm

In addition, in the peripheral area illustrated in FIG. 6A, the value ofthe transmission astigmatism is not large. That is, in the distributionillustrated in FIG. 6A, an area having the transmission astigmatismequal to 1.50 D does not show in the area “b” surrounded by a circle inthe distribution of the transmission astigmatism, which is the lateralarea illustrated in FIG. 4A.

That is, the value of the transmission astigmatism in the area “b”surrounded by a circle in the conventional design is 1.50 D or more, andthe value of the transmission astigmatism in the embodiment is less than1.50 D. As a result, it can be said that the embodiment is an improvedlens.

(5-2. Comparison of Finally Obtained Lens States Between ConventionalDesign and Embodiment)

Next, the design of the finally obtained lens will be described based onthe distribution of the transmission average refractive power as thetarget distribution and the distribution of the transmissionastigmatism. Then, the comparison of the distributions of thetransmission astigmatism of the finally obtained lens in theconventional design and the embodiment is illustrated in FIGS. 7A and7B.

Note that a double-sided composite progressive lens is used as a surfacestructure of the finally obtained lens. Other various conditions are asfollows. The specific design contents will be described in the column of(design method of progressive addition lens) described later.

-   -   Inward adjustment amount: 2.5 mm    -   Refractive index: 1.60    -   Corneal-lens apex distance (CVD): 12.0 mm    -   Distance from apex of corneal to center of cycloduction: 13.0 mm    -   Interpupillary distance (PD): 64.0 mm    -   Anteversion angle: 10.0°    -   Front angle (JIS B7281:2003): 0.0°

Hereinafter, unless otherwise specified, various conditions for thefinally obtained lens are the same. However, the present invention isnot limited to these conditions.

FIGS. 7A and 7B are diagrams illustrating the comparison of thedistributions of the transmission astigmatism finally obtained in anexample of the embodiment and the conventional design. By referring tothe area “a” of both distributions of the transmission astigmatism, itcan be seen that the clear visual field range in the near portion of theembodiment is wider than the conventional example even in the finallyobtained lens.

According to the distribution of the transmission astigmatism of theembodiment, the width of the clear visual field range is 11.13 mm aty=−14.0 mm (a1) and 15.00 mm at y=−20.0 mm (a2).

In the conventional design, the width is 7.74 mm at y=−14.0 mm (a1), and10.16 mm at y=−20.0 mm (a2).

Also, in FIG. 7A, the lateral area does not show a large astigmatismvalue. As far as the area “b” surrounded by a circle in the distributionof transmission astigmatism is viewed, the area in which thetransmission astigmatism of the lateral area is 1.75 D in FIG. 7B hardlyappears in the corresponding distribution in FIG. 7A.

That is, the value of the transmission astigmatism in the area “b”surrounded by a circle in the conventional design exceeds 1.75 D ormore, and the value of the transmission astigmatism of the correspondingarea in the embodiment is almost less than 1.75 D.

As described above, according to the embodiment, a width or an area ofthe clear visual field range in the near portion can be expanded.Therefore, the progressive addition lens of the embodiment can suppressthe blur that was conventionally felt by the wearer.

5-3. Addition Pattern of Transmission Astigmatism

Furthermore, the method for extending such transmission astigmatism notonly along the meridian and/or main line of sight but also over theentire design surface will be described along three patterns illustratedin FIGS. 8, 10, and 12.

(5-3-1. Pattern 1)

The pattern 1 is a pattern in which the astigmatism adjustment area R(see FIG. 2) of the progressive addition lens is located below thehorizontal line HL (see FIG. 2) and is a fan-shaped area that furtherextends downward.

FIG. 8 is a diagram illustrating the pattern 1 in which the transmissionastigmatism is given to the specific area on the design surface. Asillustrated on the right of FIG. 8, the addition of the transmissionastigmatism can be achieved at least at the near portion measurementreference point N. Specifically, the transmission astigmatism of 0.50 Dis given to a portion corresponding to point N on the lens.

The design surface with a diameter of 60 mm is illustrated on the leftof FIG. 8. FP is a point corresponding to a fitting point or eye point(hereinafter, this point is simply referred to as point FP). GC meansthe geometric center.

The change in transmission astigmatism along the meridian is illustratedon the right of FIG. 8, and its position corresponds to the figure onthe left. The vertical axis on the right of FIG. 8 indicates a position(mm) in a y direction, and the horizontal axis indicates thetransmission astigmatism [D]. When y is in a positive area, thetransmission astigmatism is not added, but when y is in a negative area,the additional amount of the transmission astigmatism continues toincrease, and reaches 0.50 D at point N and continues to increase.

The astigmatism is given to a fan-shaped area AS_add surrounded by arce-d-f, line segment e-GC, and line segment f-GC. The area “AS_add” iscontrolled by an angle α that is formed by the line segment e-GC and theline segment f-GC.

The transmission astigmatism is not given to an area “AS_0” (semicirclesurrounded by arc a-b-c and line segment a-c) in the upper half of thelens.

There are two fan-shaped areas “As_int”. One “As_int” is surrounded bythe arc ae, the line segment a-GC, and the line segment e-GC, and theother “As_int” is surrounded by the arc cf, the line segment c-GC, andthe line segment f-GC. The fan-shaped area “As_int” is an area where thearea “AS_add” and the area “AS_0” are interpolated. Therefore, theastigmatism smaller than 0.50 D is given to the transmission astigmatismof the interpolated area.

In other words, by imposing one constraint on the transmissionastigmatism on one point, for an eye, it is possible to obtain acircular fan shape indicating the area to which the transmissionastigmatism is added. Obviously, the transmission astigmatism canactually be provided at any point in the area (or on the line) describedabove, and thus can be given to a plurality of points.

The parameters used in pattern 1 are the additional amount of thetransmission astigmatism and the angle α that controls the range of thearea to which the astigmatism is added. The additional amount of thetransmission astigmatism is 0.50 D and the angle α is 30°. The value ofthe angle α may be any angle within 15° to 45°.

FIGS. 9A to 9D are diagrams illustrating an example of the result ofapplying the pattern 1 to the conditions (VP<HP) of the embodiment.

FIG. 9A illustrates the distribution of the transmission averagerefractive power corresponding to the pattern 1 when vertical refractivepower (VP)<horizontal refractive power (HP) in the intermediate portionand the near portion.

FIG. 9B is a diagram illustrating an example of the distribution of thetransmission astigmatism corresponding to the pattern 1 when verticalrefractive power (HP)<horizontal refractive power (VP) in theintermediate portion and the near portion.

Comparing the conventional design (FIG. 4A) and the embodiment (FIG.9B), when looking at the area “a” of the distribution of thetransmission astigmatism, it can be seen that the clear visual fieldrange in the near portion illustrated in FIG. 9B is wider than theconventional design.

Looking at an ◯ area with sign “b” of both the distributions of thetransmission astigmatism, in the distribution of the transmissionastigmatism illustrated in FIG. 9B, the peripheral area has thetransmission astigmatism of 1.50 D, and the value of transmissionastigmatism is small. The area occupied by the astigmatism of 1.50 D issmaller than the conventional design.

The width of the clear visual field area in the transmission astigmatismof pattern 1 of the embodiment is 10.65 mm at y=−14.0 mm (a1) and 15.97mm at y=−20.0 mm (a2).

In the conventional design, the width is 8.30 mm at y=−14.0 mm (a1), and10.00 mm at y=−20.0 mm (a2).

FIG. 9C is a diagram illustrating an example of the changes in thevertical refractive power, the horizontal refractive power, and theaverage refractive power corresponding to the pattern 1 along themeridian. According to FIG. 9C, at least in the near portion, thevertical refractive power is smaller than the horizontal refractivepower.

FIG. 9D is a diagram illustrating an example of the change in thetransmission astigmatism corresponding to the pattern 1 along themeridian. FIG. 9D illustrates that transmission astigmatism isintentionally given along the meridian in the intermediate portion andthe near portion.

(5-3-2. Pattern 2)

Pattern 2 is a pattern in which the astigmatism adjustment area R (seeFIG. 2) of the progressive addition lens is located below the horizontalline HL (see FIG. 2). Note that the same contents as the pattern 1 willbe omitted.

FIG. 10 is a diagram illustrating pattern 2 in which the transmissionastigmatism is given to the specific area on the design surface. Asillustrated on the right of FIG. 10, the transmission astigmatism isadded to the portion corresponding to point N which is one near portionmeasurement reference point, and as a result, the transmissionastigmatism is given to almost the lower half of the design surface.

The astigmatism is given to an area “AS_add” surrounded by arc g-d-h andline segment g-h. In the area of the “AS_add”, the value of thetransmission astigmatism is 0.50 D. The transmission astigmatism is notgiven to the area “AS_0” (semicircle surrounded by arc a-b-c and linesegment a-c) in the upper half of the lens. A rectangle such as “AS_int”surrounded by points a, c, h, and g is an area where the area “AS_add”and the area “AS_0” are interpolated. Therefore, the astigmatism smallerthan 0.50 D is given to the intrinsic astigmatism of the interpolatedarea.

FIGS. 11A to 11D are diagrams illustrating an example of the result ofapplying the pattern 2 to the conditions (VP<HP) of the embodiment.

FIG. 11A illustrates the distribution of the transmission averagerefractive power corresponding to the pattern 2 when vertical refractivepower (VP)<horizontal refractive power (HP) in the intermediate portionand the near portion.

FIG. 11B illustrates the distribution of the transmission astigmatismcorresponding to the pattern 2 when vertical refractive power(VP)<horizontal refractive power (HP) in the intermediate portion andthe near portion.

Comparing the conventional design (FIG. 4A) and the embodiment (FIG.11B), when looking at the area “a” of the distribution of thetransmission astigmatism, it can be seen that the clear visual fieldrange in the near portion illustrated in FIG. 11B is wider than theconventional design.

Looking at the ◯ area with the “b” of the distribution of transmissionastigmatism, an area of astigmatism 1.50 D exists in the distribution ofthe transmission astigmatism in the conventional design, but the area ofastigmatism 1.50 D does not appear in the distribution of transmissionastigmatism illustrated in FIG. 11B.

The width of the clear visual field range in the transmissionastigmatism illustrated in FIG. 11B is 10.65 mm at y=−14.0 mm (a1) and13.55 mm at y=−20.0 mm (a2).

In the conventional design, the width is 8.30 mm at y=−14.0 mm (a1), and10.00 mm at y=−20.0 mm (a2).

FIG. 11C illustrates the changes in the vertical refractive power, thehorizontal refractive power, and the average refractive powercorresponding to the pattern 2 along the meridian. According to FIG.11C, at least in the near portion, the vertical refractive power issmaller than the horizontal refractive power.

FIG. 11D illustrates the change in the transmission astigmatism alongthe meridian corresponding to the pattern 2. FIG. 11D illustrates thattransmission astigmatism is intentionally given along the meridian inthe intermediate portion and the near portion.

(5-3-3. Pattern 3)

Pattern 3 is a case where the astigmatism adjustment area R (see FIG. 2)of the progressive addition lens includes an area that is located belowthe horizontal line HL (see FIG. 2) and has a fixed width in thehorizontal direction.

FIG. 12 is a diagram illustrating pattern 3 in which the transmissionastigmatism is given to the specific area on the design surface. In FIG.12, the astigmatism is represented on a curvature basis, and thetransmission astigmatism is added to the portion corresponding to pointN which is one near portion measurement reference point, so thetransmission astigmatism is given to a specific area.

The design surface with a diameter of 60 mm is illustrated on the leftof FIG. 12. The figure on the right of FIG. 12 illustrates a change indifference between horizontal curvature C-h and vertical curvature C-vin the transmission along the meridian, and the positional relationshipcorresponds to the figure on the left.

In the figure on the right of FIG. 12, the vertical axis is a position[mm] in a y direction, and the horizontal axis is a difference incurvature. In the area where y is positive, the difference between thecurvature C-h and the curvature C-v is almost zero, that is, thetransmission astigmatism is not added.

The astigmatism is given to the area “AS_add” surrounded by arc g-d-r,line segment r-s, line segment s-p, and line segment p-g. In the area“AS_add”, the transmission astigmatism can be achieved at least at pointN. For example, the transmission astigmatism of 0.50 D is provided to aportion corresponding to the point N on the lens.

In pattern 3, the transmission astigmatism is added by controlling thecurvature using a spline function. A small circle “cp” in the figure onthe left of FIG. 12 is the control point of the spline function. Most ofthe control points are set a near meridian. Further, in this pattern,the control points are also arranged on a tangent line between points aand c.

FIGS. 13A to 13D are diagrams illustrating an example of the result ofapplying the pattern 3 to the conditions (HP<VP) of the embodiment.

FIG. 13A illustrates the distribution of the transmission averagerefractive power corresponding to the pattern 3 when vertical refractivepower (VP)<horizontal refractive power (HP) in the intermediate portionand the near portion.

FIG. 13B illustrates the distribution of the transmission astigmatismcorresponding to the pattern 3 when vertical refractive power(VP)<horizontal refractive power (HP) in the intermediate portion andthe near portion.

Comparing the conventional design (FIG. 4A) and the embodiment (FIG.13B), when looking at the area “a” of the distribution of thetransmission astigmatism, it can be seen that the clear visual fieldrange in the near portion illustrated in FIG. 13B is wider than theconventional design.

In the distribution of the astigmatism illustrated in FIG. 13B, lookingat the circular area with “b” in the distribution of the transmissionastigmatism, there is the area having the transmission astigmatism of1.50 D, but the transmission astigmatism in the surrounding area issmall, and the ratio occupied by the area of 1.50 D is smaller thanconventional design.

The width of the clear visual field range in the distribution of thetransmission astigmatism illustrated in FIG. 13B is 9.91 mm at y=−14.0mm (a1) and 13.55 mm at y=−20.0 mm (a2).

In the conventional design, the width is 8.30 mm at y=−14.0 mm (a1), and10.00 mm at y=−20.0 mm (a2).

FIG. 13C illustrates the changes in the vertical refractive power, thehorizontal refractive power, and the average refractive powercorresponding to the pattern 3 along the meridian. According to FIG.13C, at least in the near portion, the vertical refractive power issmaller than the horizontal refractive power.

FIG. 13D illustrates the change in the transmission astigmatism alongthe meridian corresponding to the pattern 3. FIG. 13D illustrates thattransmission astigmatism is intentionally given along the meridian inthe intermediate portion and the near portion.

6. Modification Example (Additional Amount of Transmission Astigmatismand Variation of ADD in Embodiment, and the Like)

This section shows the comparison of the additional amount of thetransmission astigmatism and variations of ADD with the conventionalprogressive addition lenses having the same ADD.

FIG. 14A is a diagram illustrating a distribution of transmissionaverage refractive power when the ADD changes to 3.00 D in theconventional progressive addition lens.

FIG. 14B is a diagram illustrating a distribution of transmissionastigmatism when the ADD changes to 3.00 D in the conventionalprogressive addition lens.

FIG. 15A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 3.00 D and theadditional amount of the transmission astigmatism changes to 0.30 D inthe embodiment.

FIG. 15B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 3.00 D and the additional amount ofthe transmission astigmatism changes to 0.30 D in the embodiment.

Comparing FIGS. 14B and 15B, in the variation of the embodiment (FIG.15B), the width or the area of the clear visual field range in the nearportion is wider as compared with the conventional case (FIG. 14B).

According to the distribution of the transmission astigmatism of theembodiment, when ADD=3.00 D, the width of the clear visual field rangeis 7.74 mm at y=−14.0 mm (a1) and 10.04 mm at y=−20.0 mm (a2).

In the conventional design, the width is 6.44 mm at y=−14.0 mm (a1), and8.06 mm at y=−20.0 mm (a2).

Table 2 shows the width of the clear visual field range according to theaddition power at y=−14.0 mm (a1), including other variations describedbelow.

Table 3 shows the width of the clear visual field range according to theaddition power at y=−20.0 mm (a2), including other variations describedbelow.

TABLE 2 Area a1 (y = −14.0 mm) Addition Power 3.00 D 2.00 D 1.00 D Widtha1 of 6.44 mm 8.30 mm 8.30 mm conventional example Width a1 of 7.74 mm9.56 mm 14.88 mm embodiment Additional amount of 0.30 D 0.20 D 0.10 Dtransmission astigmatism

TABLE 3 Area a2 (y = −20.0 mm) Addition Power 3.00 D 2.00 D 1.00 D Widtha2 of 8.06 mm 10.00 mm 10.00 mm conventional example Width a2 of 10.04mm 11.74 mm 16.94 mm embodiment Additional amount of 0.30 D 0.20 D 0.10D transmission astigmatism

FIG. 16A is a diagram illustrating a distribution of transmissionaverage refractive power when the ADD changes to 1.00 D in theconventional progressive addition lens.

FIG. 16B is a diagram illustrating a distribution of transmissionastigmatism when the ADD changes to 1.00 D in the conventionalprogressive addition lens.

FIG. 17A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 1.00 D and theadditional amount of the transmission astigmatism changes to 0.10 D inthe embodiment.

FIG. 17B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 1.00 D and the additional amount ofthe transmission astigmatism changes to 0.10 D in the embodiment.

Comparing FIGS. 16B and 17B, in the variation of the embodiment (FIG.17B), the width or the area of the clear visual field range in the nearportion is wider as compared with the conventional case (FIG. 16B).

According to the distribution of the transmission astigmatism of theembodiment, when ADD=1.00 D, the width of the clear visual field rangeis 14.88 mm at y=−14.0 mm (a1) and 16.94 mm at y=−20.0 mm (a2).

In the conventional design, the width is 13.54 mm at y=−14.0 mm (a1),and 15.26 mm at y=−20.0 mm (a2).

FIG. 18A is a diagram illustrating the distribution of the transmissionaverage refractive power when the ADD changes to 2.00 D and theadditional amount of the transmission astigmatism changes to 0.20 D inthe embodiment.

FIG. 18B is a diagram illustrating the distribution of the transmissionastigmatism when the ADD changes to 2.00 D and the additional amount ofthe transmission astigmatism changes to 0.20 D in the embodiment.

FIGS. 5B and 18B, which illustrate the distribution of transmissionaverage refractive power when ADD is 2.00 D in the conventionalprogressive addition lens, are compared. As a result, in the variationof the embodiment (FIG. 18B), the width or the area of the clear visualfield range in the near portion is wider as compared with theconventional case (FIG. 5B).

According to the distribution of the transmission astigmatism of theembodiment, when ADD=2.00 D, the width of the clear visual field rangeis 9.56 mm at y=−14.0 mm (a1) and 11.74 mm at y=−20.0 mm (a2).

In the conventional design, the width is 8.30 mm at y=−14.0 mm (a1), and10.00 mm at y=−20.0 mm (a2).

In view of each diagram in the present application related to thedistribution of the transmission astigmatism, an absolute value of achange amount Δ[D] from a value of transmission astigmatism at ameasurement reference point F of the distance portion to a value oftransmission astigmatism at a measurement reference point N of the nearportion is preferably 0.07 to 0.24 times the addition power ADD[D]. Allof the above modification examples fall within this range. Note that therange of the change amount Δ[D] is more preferably 0.10 times to 0.20times the amount of addition power ADD[D], and particularly preferably0.12 to 0.15 times.

The background of obtaining the knowledge regarding the above changeamount Δ will be described.

The present inventor has conceived the method for adding thetransmission astigmatism from the measurement reference point F of thedistance portion to the measurement reference point N of the nearportion while using the transmission design and a method for determiningthe value of the transmission astigmatism to be added according to theaddition power ADD.

Obviously, the method increases the transmission astigmatism at themeridian and measurement reference point N, but can mitigate the sharpchange in the transmission astigmatism. As a result, it can beacknowledged that the clear visual field range with the transmissionastigmatism of 0.50 D or less can be obtained more widely, and themeridian and the measurement reference point N can be included in theclear visual field range.

As illustrated in FIG. 2, the change amount Δ[D] indicates theincrement/decrement (=Δ1-Δ2) from the value Δ2 of the transmissionastigmatism at the measurement reference point F (reference numeral 16in FIG. 2) of the distance portion to the value Δ1 of the transmissionastigmatism at the measurement reference point N of the near portion.Note that the change amount Δ[D] may be defined as the maximumadditional amount of the transmission astigmatism.

In addition, the absolute value of the change amount Δ[D] is set to 0.07to 0.24 times the addition power ADD [D]. The setting of the changeamount Δ[D] can be suitably applied to a spectacle lens having the sameproduct name (design series). As a result, when the wearer reselects thespectacle lens of the same brand name (design series) of the samespectacle lens manufacturer and remakes the spectacles with the additionpower ADD[D] changed, it is possible to suppress blurring, shakingfeeling, distortion, and the like due to the change of the spectaclelens.

Based on the above findings, the provisions related to the above changeamount Δ have been conceived.

7. Effect According to One Aspect of the Present Invention

As described above, regardless of the embodiment and any one ofcombinations of patterns 1 to 3, the clear visual field range of thenear portion is expanded as compared with the conventional example, anddefects such as blurring, shaking feeling, and distortion can beimproved. This means that in the distribution of the transmissionastigmatism, the surface shape of the near portion and the intermediateportion is adjusted so that the transmission astigmatism is added to thecolumnar refractive power (for example, astigmatic power) given to apoint corresponding to the distance portion measurement reference pointF on at least the main line of sight of the intermediate portion and thenear portion.

According to an embodiment, it is also preferable that the rate ofchange in the difference at the portion where the difference between thevertical refractive power and the horizontal refractive power decreasesin the vertical direction is set to be different from the rate of changein the difference at the portion where the difference between thevertical refractive power and the horizontal refractive power increases.

As illustrated in FIG. 2, the near portion is located below thehorizontal line connecting positions of two hidden marks, and theastigmatism adjustment area that adjusts the surface shape of the nearportion and the intermediate portion is located below the horizontalline as illustrated in FIGS. 8, 20, and 22. As a result, the wearingfeeling felt by the wearer in the intermediate portion and the nearportion can be further improved.

In this case, as illustrated in FIG. 10, the astigmatism adjustment areais preferably a fan-shaped area that extends toward the lower side onthe lower side of the horizontal line. As a result, the wearing feelingfelt by the wearer in the intermediate portion and the near portion canbe further improved.

Further, as illustrated in FIG. 12, the astigmatism adjustment areapreferably includes an area having a fixed width in the horizontaldirection on the lower side of the horizontal line. As a result, thewearing feeling felt by the wearer in the intermediate portion and thenear portion can be further improved.

The progressive addition lens of the present invention and the designmethod thereof have been described in detail above, but the progressiveaddition lens of the present invention and the design method thereof arenot limited to the above embodiment and may be variously improved andchanged without departing from the gist of the present invention.

For example, a technical idea of the present invention is also reflectedto a method for manufacturing a progressive addition lens including adesign step which is the design method described so far, and

a manufacturing step for manufacturing a progressive addition lens basedon the design step.

In addition, the technical idea of the present invention is reflected toa lens group configured of a plurality of progressive addition lensincluding a near portion for viewing a near distance, a distance portionfor viewing a distance farther than the near distance, and anintermediate portion provided between the near portion and the distanceportion and having a progressive refraction function,

in which in each progressive addition lens, the transmission astigmatismis added to the near portion and the intermediate portion of thedistance portion, the near portion, and the intermediate portion.

It goes without saying that the preferred examples described in thepresent specification may be applied to each of these aspects.

As a result, the advantage is obtained by adding the transmissionastigmatism to the intermediate portion and the near portion. Thisadvantage includes, for example, the expansion of the clear visual fieldrange in the near portion, the reduction in the transmission astigmatismon both sides of the intermediate portion and the near portion, thereduction of the rate of change of the astigmatism, and the like.

SUMMARY

The following is a summary of the “progressive addition lens and designmethod thereof” disclosed in this disclosure.

An embodiment of the present disclosure is as follows.

A progressive addition lens, including: a near portion for viewing anear distance, a distance portion for viewing a distance farther thanthe near distance, and an intermediate portion provided between the nearportion and the distance portion and having a progressive refractionfunction,

in which the transmission astigmatism is added to the near portion andthe intermediate portion of the distance portion, the near portion, andthe intermediate portion, and

in the near portion and intermediate portion to which the transmissionastigmatism is added, the progressive addition lens further includes aportion in which an amount of horizontal refractive power is greaterthan an amount of vertical refractive power after subtracting therefractive power for astigmatism correction.

REFERENCE SIGNS LIST

-   MP Average refractive power-   AS Transmission astigmatism-   VP Vertical refractive power-   HP Horizontal refractive power-   ADD Addition power-   AX Cylindrical axis-   Tf Tangential transmission refractive power (T) of distance vision-   Tn Tangential transmission refractive power (T) of near vision-   Sf Sagittal transmission refractive power (S) of distance vision-   Sn Sagittal transmission refractive power (S) of near vision-   GC Geometric center-   F Distance portion measurement reference point-   FP Fitting point-   N Near portion measurement reference point-   AS_0 Area where transmission astigmatism is not given-   AS_int Area where area of transmission astigmatism and area with    transmission astigmatism of zero are interpolated-   AS_add Area where transmission astigmatism is given

1. A progressive addition lens, comprising: a near portion for viewing anear distance; a distance portion for viewing a distance farther thanthe near distance; and an intermediate portion provided between the nearportion and the distance portion and having a progressive refractionfunction, wherein the transmission astigmatism is added to the nearportion and the intermediate portion of the distance portion, the nearportion, and the intermediate portion, and in the near portion andintermediate portion to which the transmission astigmatism is added, theprogressive addition lens further includes a portion in which an amountof horizontal refractive power is greater than an amount of verticalrefractive power after subtracting the refractive power for astigmatismcorrection.
 2. The progressive addition lens according to claim 1,wherein the transmission astigmatism having an absolute value exceedingzero and 0.25 D or less is added to the near portion and theintermediate portion.
 3. The progressive addition lens according toclaim 1, wherein an absolute value of the value of the transmissionastigmatism at the measurement reference point F of the distance portionafter subtracting the refractive power for astigmatism correction is0.12 D or less.
 4. The progressive addition lens according to claim 1,wherein an amount of an absolute value of a change amount Δ[D] from avalue of transmission stigmatism at a measurement reference point F ofthe distance portion to a value of transmission astigmatism at ameasurement reference point N of the near portion is 0.07 to 0.24 timesthe addition power ADD[D].
 5. The progressive addition lens according toclaim 1, wherein the transmission refractive power is added togetherwith the transmission astigmatism.
 6. A design method of a progressiveaddition lens including a near portion for viewing a near distance, adistance portion for viewing a distance farther than the near distance,and an intermediate portion provided between the near portion and thedistance portion and having a progressive refraction function, thedesign method of a progressive addition lens comprising: adding thetransmission astigmatism to the near portion and the intermediateportion of the distance portion, the near portion, and the intermediateportion, wherein in the near portion and intermediate portion to whichthe transmission astigmatism is added, the progressive addition lensfurther includes a portion in which an amount of vertical refractivepower is greater than an amount of horizontal refractive power aftersubtracting the refractive power for astigmatism correction.
 7. Theprogressive addition lens according to claim 2, wherein an absolutevalue of the value of the transmission astigmatism at the measurementreference point F of the distance portion after subtracting therefractive power for astigmatism correction is 0.12 D or less.
 8. Theprogressive addition lens according to claim 2, wherein an amount of anabsolute value of a change amount Δ[D] from a value of transmissionstigmatism at a measurement reference point F of the distance portion toa value of transmission astigmatism at a measurement reference point Nof the near portion is 0.07 to 0.24 times the addition power ADD[D]. 9.The progressive addition lens according to claim 3, wherein an amount ofan absolute value of a change amount Δ[D] from a value of transmissionstigmatism at a measurement reference point F of the distance portion toa value of transmission astigmatism at a measurement reference point Nof the near portion is 0.07 to 0.24 times the addition power ADD[D]. 10.The progressive addition lens according to claim 7, wherein an amount ofan absolute value of a change amount Δ[D] from a value of transmissionstigmatism at a measurement reference point F of the distance portion toa value of transmission astigmatism at a measurement reference point Nof the near portion is 0.07 to 0.24 times the addition power ADD[D]. 11.The progressive addition lens according to claim 2, wherein thetransmission refractive power is added together with the transmissionastigmatism.
 12. The progressive addition lens according to claim 3,wherein the transmission refractive power is added together with thetransmission astigmatism.
 13. The progressive addition lens according toclaim 4, wherein the transmission refractive power is added togetherwith the transmission astigmatism.
 14. The progressive addition lensaccording to claim 7, wherein the transmission refractive power is addedtogether with the transmission astigmatism.
 15. The progressive additionlens according to claim 8, wherein the transmission refractive power isadded together with the transmission astigmatism.
 16. The progressiveaddition lens according to claim 9, wherein the transmission refractivepower is added together with the transmission astigmatism.
 17. Theprogressive addition lens according to claim 10, wherein thetransmission refractive power is added together with the transmissionastigmatism.